The present invention relates to a memory disk apparatus and, more particularly, to a memory disk apparatus for recording data on tracks of a memory disk or for reproducing recorded data on the tracks while rotating the memory disk and a head relative to each other.
In a document filing system, an optical disk apparatus is used. The optical disk apparatus includes an optical memory disk having a number of spiral or concentric tracks. Data is recorded on or recorded data is reproduced from the tracks of the rotating optical disk. For example, a document is two-dimensionally scanned with light, and optical image data of the document is photoelectrically converted into electrical image data. The electrical image data is recorded on the tracks of the optical memory disk. The recorded data is retrieved and is reproduced as hard or soft copy, as needed. Recording or reproducing data on or from tracks of an optical memory disk is performed by an optical head which is arranged in the proximity of the surface of the rotating optical memory disk. The optical head is mounted on a carriage of a motor which is linearly moved along the radial direction of the optical disk. A position detector is arranged to detect the position of the optical head relative to the position of the carriage of the linear motor. The position detector has an optical linear scale unit. The optical linear scale unit includes first and second lattice pattern members which are sequentially arranged between a photoemissive element and a photoelectric element. The first lattice pattern member is coupled to the carriage for movement therewith. The second lattice pattern member is fixed in position and serves as an optical filter.
In the apparatus of the configuration described above, the linear motor is moved while the position of the optical head is detected by the position detector from the position of the carriage. Thus, the optical head can be positioned at a desired track within 0.1 mm.
In the conventional optical memory disk described above, when data is recorded on or reproduced from the disk, the disk is rotated at a given rotational speed and the data is recorded on or reproduced from tracks of the disk in units of sectors. Such data recording or reproduction is performed while the peripheral speed is increased as the head moves radially outward. Therefore, the recording density is lowered toward the outer periphery of the disk, and the overall recording density cannot be improved.